reader: do not map the pages as writable

it is somehow insecure and useless to map the pages of the bitmap as
writable if we only want to read data from it.

Signed-off-by: Olivier Gayot <duskcoder@gmail.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/stegmp.c b/stegmp.c
index c80075c..6584e81 100644
--- a/stegmp.c
+++ b/stegmp.c
@@ -151,8 +151,8 @@ static int stegmp(const char *bmp_file, FILE *input)
     }
 
     fstat(fileno(fh), &stat);
-    addr = mmap(NULL, stat.st_size, PROT_READ | PROT_WRITE, MAP_PRIVATE,
-            fileno(fh), 0);
+    addr = mmap(NULL, stat.st_size, PROT_READ | ((input) ? PROT_WRITE : 0),
+            MAP_PRIVATE, fileno(fh), 0);
 
     if (addr == MAP_FAILED) {
         fprintf(stderr, "%s: %m\n", bmp_file);